section 743.1(4)


743.1(4) Where a person is sentenced to imprisonment in a penitentiary while the person is lawfully imprisoned in a place other than a penitentiary, that person shall, except where otherwise provided, be sent immediately to the penitentiary, and shall serve in the penitentiary the unexpired portion of the term of imprisonment that that person was serving when sentenced to the penitentiary as well as the term of imprisonment for which that person was sentenced to the penitentiary.